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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS
for the guidance of teachers
0620 CHEMISTRY
0620/33
Paper 3 (Extended Theory), maximum raw mark 80
This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of
the examination. It shows the basis on which Examiners were instructed to award marks. It does not
indicate the details of the discussions that took place at an Examiners’ meeting before marking began,
which would have considered the acceptability of alternative answers.
Mark schemes must be read in conjunction with the question papers and the report on the
examination.
•
CIE will not enter into discussions or correspondence in connection with these mark schemes.
CIE is publishing the mark schemes for the October/November 2010 question papers for most IGCSE,
GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level
syllabuses.
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MARK SCHEME for the October/November 2010 question paper
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International General Certificate of Secondary Education
Page 2
1
Mark Scheme: Teachers’ version
IGCSE – October/November 2010
Syllabus
0620
Paper
33
(a) to complete the outer shell (of oxygen) / full outer or valence shell / 8 (electrons) in outer
shell / Noble gas structure / to complete outer shell / to complete the octet
ignore reference to hydrogen atoms / reference to accepting / sharing or gaining electrons [1]
(b) loses (one) electron
not loses electrons
[1]
(c) opposite charges attract / electrostatic attraction / positive attracts negative / + and – attract
[1]
(d) in solid ions cannot move / flow / no free ions / ions in a lattice
in solution ions can move / flow / mobile ions / ions free (to move)
[1]
[1]
[Total: 5]
2
(a) 23p 23e 28n
23p 20e 28n
23p 23e 27n
[1]
[1]
[1]
(b) (i) (contains) iron
cond with other element(s) / compounds / suitable named element
if iron is absent = 0
[1]
[1]
(ii) mild steel
[1]
cars / fridges / white goods / construction etc.
[1]
credit any sensible suggestion e.g. roofing, nails, screws, radiators
or
stainless steel
[1]
cutlery / chemical plant / jewellery / (kitchen) utensils / named kitchen utensil / in cars /
surgical equipment / car exhausts etc.
[1]
not vanadium steel (this is in the question)
(c) (i) V2O3
VO2
[1]
[1]
(ii) add sodium hydroxide(aq) or other named alkali
not ammonia
cond vanadium(IV) oxide dissolves / reacts
filter (to remove vanadium(III) oxide)
[1]
[1]
[1]
[Total: 12]
© UCLES 2010
Page 3
3
Mark Scheme: Teachers’ version
IGCSE – October/November 2010
Syllabus
0620
Paper
33
(a) (i) silver, tin (cobalt and magnesium not possible to decide)
for silver less reactive then tin = 1
[2]
(ii) magnesium and cobalt salt / compound / ions
or
cobalt and magnesium salt / compound / ions
[1]
(iii) Sn + 2Ag+ Sn2+ + 2Ag
all species correct = 1
balancing = 1
Sn to Sn2+ oxidation (can be written separately or as a correct half-equation)
(b) no reaction
Mg(OH)2 MgO + H2O
[2]
[1]
[1]
[1]
accept multiples
(c) (i) it forms positive ions / loses or gives electrons
electrons move / flow from this electrode / enter the circuit / electrons flow from
negative to positive (so it is negative)
[1]
[1]
(ii) bigger voltage of Zn/Cu cell than Sn/Cu cell
or
zinc is negative relative to tin (in the third cell)
[1]
(iii) magnesium / more reactive metal (must be named) instead of zinc
not anything above calcium in the reactivity series
or
silver / less reactive metal (must be named) instead of copper
or
use (more) concentrated acid
[1]
(iv) polarities correct that is Zn - and Sn +
0.6 V
[1]
[1]
[Total: 14]
4
(a) (i) H2 on RHS
ignore any other species on RHS
rest of equation fully correct i.e. 2H+ + 2e H2
(ii) H+ removed / escapes / discharged / used up / reduced
(equilibrium) moves to RHS / more water molecules ionise or
dissociate / forward reaction favoured
[1]
[1]
[1]
[1]
(iii) oxygen / O2
not O
[1]
(iv) carbon / graphite / platinum (electrode)
[1]
(b) (i) to make ammonia / in petroleum processing / balloons / rocket fuel / fuel for cars /
hardening of fats / fuel cells / fuel (unqualified) / making hydrochloric acid
[1]
(ii) to sterilise / disinfect it / kill bacteria / bugs / microbes / micro-organisms / germs
© UCLES 2010
[1]
Page 4
Mark Scheme: Teachers’ version
IGCSE – October/November 2010
Syllabus
0620
Paper
33
(c) (i) (reference to) volume and time / how long it takes
[1]
(ii) carry out experiment with different intensities of light / one in light and one in
dark / repeat experiment in reduced light
measure new rate which would be faster or slower depending on light intensity
[1]
[1]
[Total: 11]
5
(a) (i) Mg + 2CH3COOH (CH3COO)2Mg + H2
correct formula of magnesium ethanoate
ignore charges
[1]
[1]
sodium ethanoate + water
[1]
(ii) ethyl ethanoate
displayed formula
[1]
[1]
(b) (i) add up to 5.8 g
[1]
(ii) moles of C atoms = 2.4/12 = 0.2
moles of H atoms = 0.2/1 = 0.2
moles of O atoms = 3.2/16 = 0.2
all three correct = 2
two correct = 1
empirical formula CHO
[2]
[1]
(iii) 116/29 = 4
C4H4O4
correct formula with no working scores both marks.
(iv) HOOCCH=CHCOOH / CH2=C(COOH)2
[1]
[1]
[2]
[Total: 13]
6
(a) (i) 6e between two nitrogen atoms (can be any combination of dots or crosses)
1 lone pair on each nitrogen atom
(ii)
[1]
[1]
SOLID
GAS
PATTERN
regular / lattice (not fixed)
random / irregular / no pattern
[1]
DISTANCE
close
far apart / spread out
[1]
MOVEMENT
vibrate / fixed / no motion
moving / translational
[1]
(b) (i) particles/molecules have more energy / move faster
[1]
collide harder / collide more frequently / more collisions / collide with more force (with the
walls)
[1]
© UCLES 2010
Page 5
Mark Scheme: Teachers’ version
IGCSE – October/November 2010
Syllabus
0620
(ii) (1) nitrogen has smaller Mr / lighter molecules / lower density
nitrogen molecules / particles move faster (than chlorine molecules)
Paper
33
[1]
[1]
(2) at higher temperature nitrogen molecules or particles (not atoms) move faster /
have more energy
[1]
[Total: 10]
7
(a) (i) lighter / light / lightweight / lower density
does not corrode / rust / oxidised
ignore cheaper / easier to mould
[1]
[1]
(ii) credit any two sensible suggestions e.g. rope / clothing / netting / string / carpets / fishing
line / fishing nets / parachutes / tyres / tents / bottles / thread / umbrellas / curtains /
toothbrushes / cassettes / video tapes
[2]
(iii) non-biodegradeable / do not rot / do not decompose / persist for years / accumulate
landfill sites limited / getting filled up
visual pollution
danger to fish / animals
(burn to form) toxic gases / harmful gases / pollutant gases / acidic gases / CO / HCl /
HF / HCN
not oxides of nitrogen / sulfur
any three
[3]
(b) (i) propene / propylene
accept prop-1-ene
not prop-2-ene
CH3-CH=CH2
double bond must be shown
[1]
[1]
(ii) correct repeat unit (one or more whole repeat units must be given)
cond continuation
(c) (i) amide / peptide / polypeptide
[1]
[1]
[1]
(ii) protein / polypeptide
[1]
(iii) H2N(CH2)6NH2
HOOC(CH2)8COOH
[1]
[Total: 15]
© UCLES 2010